Device for obtaining mechanical material deformations by means of compression waves



3,41 7,588 ATIOINS S. SCHMIDT Dec. 24, 1968 DEVICE FOR OBTAININGMECHANICAL MATERIAL DEFORM BY MEANS OF COMPRESSION WAVES 4 Sheets-Sheet1 Filed Feb. 23. 1966 INVENTOR.

SIEGFRIED SCHMIDT BY a K AGEN Dec. 24, 1968 s. SCHMIDT 3,417,588

DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS BY MEANS OFCOMPRESSION WAVES 4 Sheets-Sheet 2 Filed Feb. 23, 1966 INVENTOR.

SIEGFRIED SCHMIDT BY AGENT Dec. 24, 1968 s SCHMIDT 3,417,588

DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS BY MEANS OFCOMPRESSION WAVES Filed Feb. 23, 1966 4 Sheets-Sheet 3 F ig.4

INVENTOR.

SIEGFRIED SCHMIDT BY jzwa AGENT Dec. 24, 1968 s. SCHMIDT 3,417,588

DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS I BY MEANS OFCOMPRESSION WAVES Filed Feb. 23, 1966 4 Sheets-Sheet 4 1% 2 Z I Q' P WThT SIEGFRIED SCHMIDT BY 2 F I AGENT United States Patent 3,417,588DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS BY MEANS OFCOMPRESSION WAVES Siegfried Schmidt, Hamburg, Germany, assignor to NorthAmerican Philips Company, Inc., New York, N.Y., a corporation ofDelaware Filed Feb. 23, 1966, Ser. No. 529,518 Claims priority,application Germany, Feb. 27, 1965, P 36,179 6 Claims. (Cl. 7256)ABSTRACT OF THE DISCLOSURE A device for producing mechanicaldeformations in a material, comprising an electric discharge chamber andspaced electrodes projecting into the chamber. The material to bedeformed is held to form one boundary surface of the chamber and aliquid layer extending between the electrodes forms the opposingboundary surface. The construction minimizes erosion of the electricdischarge chamber. In a second embodiment the liquid layer is formed onthe surface of a rotating disc which thereby continuously replenishesthe liquid layer forming the boundary surface.

The invention relates to a device for producing mechanical materialdeformations by means of compression waves which are obtained by meansof electrical spark discharges in a discharge space of which at leastone of the boundary walls is constituted by the material to beprocessed.

Producing compression waves by spark discharges is known. In order touse the compression wave produced by a spark discharge as effectively aspossible the discharge; space should be limited. The material of theWall used for the said space which, with the exception of the electrode,usually consists of an insulator, is stressed rather heavily inparticular when the spark substantially travels along said wall (slidingspark). Even if insulators, for example, aluminum oxide, which are verysuitable for the said purpose, are used the wear is large so that as aresult the use of such sliding spark gaps is restricted. If theinsulator consists of organic material (for examplepolyethyleneterephthalate) which during the stress by the sparkdischarge develops gas which is favourable for producing the pressure,the wear of course, is even larger. To obtain nevertheless a usefuldevice, the wear should be distributed over a larger area. This isobtained by using comparatively large rotating discs or hollow cylindersof the insulating material in question which are arranged so that eachtime only a very small part of the insulator surface constitutes a wallof the spark discharge space, a new part of the insulator surface beingeach time chosen as a result of the rotation. However, this measure cannot prevent either that the insulator has to be replaced rather often orhas to be processed again.

It is the object of the invention to decrease the Wear of the insulatorconsiderably. According to the invention this is attained in that in adevice of the type mentioned above one of the boundary surfaces of thedischarge space is constituted by the surface of a liquid.

This provides the advantage that during operation liquid can easily bereplenished. Instead of undesired wear only "ice a low liquidconsumption occurs. Moreover, by using readily vaporizing liquids theknown effect of promoting the production of pressure can be obtained ina simple manner. Pure water can particularly readily be used as theliquid; it is cheap, safe and leaves no residue. As a result of apossible low conductivity the spark gap may exhibit even when notoperative, a relatively low resistance. This, however, is not disturbingat all if the sparking voltage is applied to the spark gap for a shorttime only. This is the case if the discharge circuit comprises a switch(for example, a spark gap switch) or if voltage is applied to the sparkgap by means of a suitable circuit each time only a short period of timebefore a discharge (for example, by controlled charging of the capacitorto be discharged). If a voltage is continuously applied to the sparkgap, which is the case if the spark gap itself also serves as a switch,and if for simplicity a controlled capacitor charge is not utilized, thecurrent flowing as a result of the resistance of the water must besupplied by the voltage source. Said current can be kept small bysuitable structural measures and by using water of a maximum purity.Said current may be used to advantage as a control current in a circuitfor controlling the liquid level.

Alternatively insulating liquids, for example, transformer oil, clopheneand the like may be used. In this case it is favourable to cause theliquid to circulate in a circulating system, which circulation in suchcircumstances, is also suitable if water is used. The circulation systemmay comprise filters or other purifying devices. Harmful impuritieswhich are formed by the spark discharges and in the absence of such acirculation system might give rise to short-circuiting of the electrodescan thus be removed. If the discharge is effected in a protective gas,for example, argon or nitrogen, readily vaporising liquids may also beused. By supplementary supply of oxygen the energy released due tocombustion of a certain amount of liquid may be used to advantage forproducing the pressure.

The use of liquids as a boundary of the discharge space has anadditional advantage, namely that the excess heat can be dissipated in asimple and effective manner. By vaporisation of the liquid acoolingeffect is obtained and, in case of circulation of the liquid, anadditional cooling is obtained by convection. In the case of largepowers it is efficacious to provide in known manner a cooler in thecirculation of the liquid.

In order that thejinvention may readily be carried into effect, a fewembodiments of the device according to the invention will now bedescribed in greater detail, by way of example, with reference to thediagrammatic drawings, in which,

FIGURE 1 is a cross-sectional view of a device employing electrodesproducing sliding sparks along a liquid surface.

FIGURE 2 is a plan view of the part of this device comprising theelectrodes.

FIGURE 3 shows a device having an insulator covered with a layer ofliquid.

FIGURE 4 is a cross-sectional view taken on the line A-B of FIGURE 3.

FIGURES 5 and 6 show a circuit arrangement for producing the sparkdischarges.

FIGURE 1 is a cross-sectional view of a device for punching holes in apaper tape or sheet 8. FIGURE 2 shows a plan view of this device havingthree spark gaps. The main electrodes 1 and the ignition electrodes 2are arranged in the bottom of a trough-shaped insulating liquidcontainer 3 filled with liquid 5. The ignition electrodes 2 just emergeabove the surface 4 of liquid 5. The surface of the liquid 5 is coveredwith a thin insulating plate 6 which, however, does not cover the spacebetween the electrodes 1 in which the discharge occurs. The perforatedstrips 7 only serve for supporting the plate 6. The plate ensures thatthe material 8 to be punched does not contact the liquid. By suitableshape of the liquid container, the surface 4 of the liquid might belimited beforehand to the space between the electrodes but this has thedrawback that, as a result of liquid consumption, the liquid level iseasily influenced. Compared with the free working surface 4, the totalupper surface of the-liquid is therefore chosen to be large. In thediagrammatic arrangement shown in FIGURE 1, the prescribed level shouldnot be higher than the lower side of the plate 6. The main electrodes 1are surrounded by insulated tubes 9 which do not cover the sides of theends of the electrodes facing the surface of the liquid. As a result ofthis, an electric current, if any, through the liquid is restricted to avalue which is as small as possible. In circumstances it may be ofadvantage to provide the greater part of the ignition electrodes 2 alsowith an insulating jacket.

The punch matrix is indicated by 11. The springs 11 force the matrix 11against the material 8 to be punched and said material is forced againstthe plate 6 so that only a very small gas-filled space 12 remains inwhich the spark discharge can form.

Devices for supplying liquid through pipes and for keeping the liquidlevel constant are known and are not shown in the drawing. The liquidlevel can very easily be controlled by means of an overflow pipe,particularly if the liquid circulates in a specially providedcirculation system. In contrast with the known devices the embodimentdescribed has the advantage that no structural difficulties occur whenseveral spark gaps operating independently of one another are arrangedin close proximity to one another.

FIGURES 3 and 4 diagrammatically show a device for producing slidingsparks along an insulator covered with a layer of liquid. In theembodiment shown the sliding sparks are used for punching. FIGURE 4 is across-sectional view of the device shown in FIGURE 3 taken on the lineA-B.

In this embodiment the insulator which bounds the spark discharge spaceconsists of a disc 23 driven by a rotating shaft 24. In this case, therotating disc 23 dips in the liquid 26 in the container 25 and thesurface of this disc is coated with a layer of liquid. The sparkdischarge which produces the compression waves occurs between the twomain electrodes 21 which are arranged on either side of the insulatordisc so that the spark slides along the insulator which is coated with alayer of liquid. The layer of liquid prevents the insulator disc 23 frombeing attacked by the spark discharge. If the sliding spark gap is alsoto be used for switching the discharge, a third electrode, an ignitionelectrode 22, is provided. A plate 27 serves as a support for thematerial 28 to be punched which is forced against the plate 27 by thesprings 29 of the punch matrix 30. The plate 27 is provided with arecess in which the disc 23 is arranged so that between the ends of theelectrodes 21 and 22 opposite to the hole in the matrix 30 a limiteddischarge space is formed. The insulator which limits the dischargespace may also be wetted in a different manner. For example, a stream ofliquid may be conducted through the insulator which in that case may bestationary, or a porous or perforated insulator may be used throughwhich the liquid required on the surface is forced.

FIGURES 5 and 6 show two electric circuit diagrams suitable foroperating spark gaps of the type as described above.

FIGURE 5 shows a circuit arrangement employing an additional circuitelement in the discharge circuit. This circuit element is, for example,a spark gap switch T, sometimes termed trigatron. A capacitor C ischarged, for example, through a resistor R by a voltage source U and theworking spark gap F constituted by the electrodes 1' and 21 respectivelyof the device shown in FIGURES 1 and 2 and 3 and 4 respectively isoperated with the energy accumulated in the capacitor. A discharge ofthe capacitor C through the spark gap F is first blocked by the' sparkgap switch T which is connected in series with the working spark gap F.Now if an ignition signal is applied to the ignition generator ZG, thelatter produces ahi gh voltage pulse which is conducted to the ignitionelectrode 2 of the spark gap switch T.

As a result of this the spark gap switch T is ignited. The capacitorvoltage which was first applied to the spark gap switch T by way of theresistor R is now suddenly applied to the working spark gap F 50 thatthe latter breaks down. The resistor R connected parallel to the sparkgap F may be present as such as a resistance of the liquid between theelectrodes or is included in the circuit as an additional circuitelement.

FIGURE 6 shows a circuit arrangement in which the working spark gap F isalso operative as a spark gap switch. Therefore the circuit arrangementcomprises the ignition electrode 2 in addition to the two mainelectrodes 1. The discharge is started, as was the case in the circuitarrangement shown in FIGURE 5, by an ignition signal at the ignitiongenerator ZG which produces a high voltage pulse which is applied to theignition electrode 2 of the working spark gap as a result of which thedischarge occurs. Since in the method described which employs a liquidbetween the electrodes, the parallel resistor R in circumstances may besmall so that it causes a disturbing discharge of the capacitorC beforethe desired spark discharge, the capacitor C is charged only a shortperiod of time before the desired main discharge. For that purpose, thecharging of the capacitor C is controlled, for example, with a circuitarrangement as shown in FIGURE 6 comprising a choke coil L, atransformer Tr, a pulse trans former U and a thyristor Th. A short timebefore the occurrence of the ignition signal the control electrode G ofthe thyristor Th receives a charging signal through the pulsetransformer U as a result of which the thyristor ignites. As a result ofthis, the capacitor C is charged inductively in known manner from thevoltage source U through the choke coil L. The transformer serves foradapting the operating voltage U of the thyristor to the desired voltageof the capacitor. As soon as the voltage across the capacitor hasreached its maximum value, the spark discharge is ignited. Thus voltageis set up at the resistor R only for a short period of time so that thelosses caused by the resistor remain low.

What is claimed is:

1. A device for producing mechanical deformations of a material,comprising means defining an electric discharge chambcr, electrode meansspaced apart and terminating within said chamber, means positioning saidmaterial to form a first boundary surface of said chamber thereby tosubject said material to the action of electric discharges in saidchamber, and means for forming a second bound-a ry surface of saiddischarge chamber extending between said spaced electrodes comprisingmeahs for supporting a liquid layer in the space between said electrodes2. A device as claimed in claim 1 wherein said first and second boundarysurfaces are in spaced confronting relationship.

3. A device as claimed in claim 1 wherein said electrodes extend throughsaid liquid layer and further comprising insulating coatings on saidelectrodes over the portions thereof extending through the said liquidlayer.

4. A device as claimed in claim 1 comprising a movable References Citedmember having a portion thereof arranged in the space UNITED STATESPATENTS between said electrode means, and means for forming a liquidlayer on the surface of said portion. 2,737,882 3/1956 Early et a1 5. Adevice as claimed in claim 4, wherein said mov- 5 3,027,791 4/1962 Earlyet 29 421 able member is a rotatable disc member having a first3,232,085 2/1966 9 72 56 peripheral portion thereof arranged in thespace between 3,266,355 8/1966 Wlnlamson 83 177 said electrode means,and a second peripheral portion thereof arranged in liquid supply means.RICHARD HERBST P r 1mm y Exammer' 6. A device as claimed in claim 1wherein said liquid 10 US. Cl. X.R. layer is an electrically circulatingliquid layer. 83177

